A theologian in the court of the Abbasid Caliph al-Muqtadir (fl. 908-932), Ahmad ibn Fadlan in the early 920s participated in a diplomatic mission from Baghdad to what is now Russia. Over the course of his journey, he encountered a number of Turkic peoples, as well another group that left a strong impression on him: the Vikings. He recorded these events in a volume that has yet to be fully translated into English; yet thanks to best-selling novelist Michael Crichton (1942-), Ibn Fadlan—at least, a fictionalized version of him—has become known to a number of Western readers.

The circumstances of Ibn Fadlan's life prior to 921 are almost entirely unknown. By judging from certain specifics in his writing style, it has been surmised that he was not an Arab, and it appears certain that prior to his departure on his...